Re: [PATCH v2 0/4] fix "rebase -i --root" corrupting root commit

[Hilco Wijbenga <hilco.wijbenga@gmail.com>]

On Tue, Jul 31, 2018 at 11:22 PM, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Tue, Jul 31, 2018 at 9:30 PM Hilco Wijbenga <hilco.wijbenga@gmail.com> wrote:
>> On Tue, Jul 31, 2018 at 12:33 AM, Eric Sunshine <sunshine@sunshineco.com> wrote:
>> > This is a re-roll of [1] which fixes sequencer bugs resulting in commit
>> > object corruption when "rebase -i --root" swaps in a new commit as root.
>> > Unfortunately, those bugs made it into v2.18.0 and have already
>> > corrupted at least one repository (a local project of mine). Patches 3/4
>> > and 4/4 are new.
>>
>> Does this also fix losing the initial commit if it is empty?
>>
>> git init ; git commit -m 'Initial commit' --allow-empty ; touch
>> file.txt ; git add file.txt ; git commit -m 'Add file.txt' ; git
>> rebase --root
>>
>> I would expect there to be 2 commits but the first one has
>> disappeared. (This usually happens with "git rebase -i --root" early
>> on in a new project.)
>
> This series should have no impact on that issue; it is fixing root
> commit object corruption, and does not touch or change how the commit
> graph is maintained or how the rebasing machinery itself works (and
> the --allow-empty stuff is part of that machinery).
>
> As Dscho is cc:'d already, perhaps he can chime in as a resident expert.
>
> By the way, what happens if you use --keep-empty while rebasing?

I was not aware of that flag. But, although I was expecting it to, if
I use it with the rebase, I don't see any different behaviour. I can't
really make out what its purpose is from "Keep the commits that do not
change anything from its parents in the result.".

But your suggestion did make me think about what behaviour I would
like to see, exactly. I like that Git removes commits that no longer
serve any purpose (because I've included their changes in earlier
commits). So I would not want to keep commits that become empty during
the rebase. What I would like to see is that commits that _start out_
as empty, are retained. Would such behaviour make sense? Or would that
be considered surprising behaviour?